Protein deficiency refers to a lack of adequate protein intake in the diet, leading to negative health effects. Proteins are essential macronutrients that play a crucial role in the growth, repair, and maintenance of tissues in the body. When individuals do not consume enough protein, they may experience symptoms such as muscle weakness, fatigue, slow wound healing, and impaired immune function. Severe protein deficiency can lead to conditions such as kwashiorkor and marasmus, which can be life-threatening if left untreated. Protein deficiency is most common in developing countries where access to adequate nutrition is limited, but it can also occur in populations with restricted diets or eating disorders. Treatment usually involves increasing protein intake through dietary changes or supplementation.